Lysosomal enzyme release has been shown to constitute a significant and constant biochemical event in the tissue regression, including tumor cell injury and cell death. Enhancement of lysosomal enzyme release favors tumor cell degradation by conventional chemotherapeutic agents and X rays. Our present studies are intended to elucidate some of the basic mechanisms in lysosomal enzyme release by various substances such as vitamin A and Trypan Blue, referred to as lysosomal labilizers. The studies will include localization of receptor sites in the cell, isolation and characterization of retinol-binding cytoplasmic proteins. Nature of the lysosomal-enzyme release phenomenon whether it reflects actual in vivo release or increased fragility of lysosomes to subsequent therapeutic procedures. Also to be studied are the mechanisms of cell surface changes induced by lysosomal labilizing agents. The adenyl cyclase-cAMP-phosphodiesterase system will be compared in normal cells and their malignant counterpart in order to determine its role in cell growth regulation.